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ASPHYXIANTS (IRRESPIRABLE GASES)
CARBON DIOXIDE (CARBONIC ACID GAS, CARBONIC
This is a heavy, colourless, inodorous gas, having a slightly acid taste.
It islTconstituent of the atmospheric air in which it exists to an extent of
0.04 per cent. A proportion of 2 or 3 per cent of carbon dioxide in air does
not produce any injurious effects except that it increases the rate and de^Jh
of respiration. A concentration of 5 per cent of carbon dioxide in air cau^s
discomfort and distressing symptoms of dyspnoea, while a concentration of
25 to 30 per cent exercises a direct toxic action on the nerve cells and is
likely to cause death. A concentration of carbon dioxide of even 0.5 per
cent in a badly ventilated and overcrowded room produces symptoms of
languor and headache, especially due to increased temperature, humidity
and stagnation. Exposure to such air for a prolonged period produces loss
of appetite, indigestion, debility and anaemia.
Carbon dioxide is given off in the process of respiration, combustion,
fermentation and putrefaction of animal matter. It forms the choke damp
or after damp of the coal mines. It is also evolved in the neighbourhood
of lime kilns on account of decomposition of carbonates. Being heavier than
air it tends to accumulate at the bottoms of old wells, damp cellars, mine
shafts, brewers' vats, grain pits, etc.
Carbon dioxide (Carbonei dioxidum) is a pharmacopoeial preparation
and stimulates the respiratory centre, when administered by inhalation in
dilutions of 5 to 7 per cent with oxygen, but as a stimulant of a depressed
respiratory centre it has practically no place. It acts as a mild rubefacient
when applied externally in the form of a solution, but in the solid form it
acts as a caustic. Solid carbon dioxide is sold in the market as " dry ice *\
and figures as a commercial refrigerant.
Symptoms.—These are heaviness in the head, throbbing of the temporal
arteries, giddiness, ringing in the ears, a sensation of oppression, muscular
weakness, mental weakness, drowsiness and insensibility passing into coma
with stertorous breathing. Death occurs from asphyxia or apoplexy. Some-
times there may be convulsions and delirium.
When inhaled in a high concentration of 60 to 80 per cent, immediate
insensibility occurs followed by death from spasm of the glottis causing
Treatment—The patient must at once be removed into the open air, and
artificial respiration should be started with inhalation of oxygen, This ought
to be assisted by galvanism and friction of the extremities. After breathing
is established, the body should be well covered with blankets* and coffee or
brandy should be administered internally. If a patient is seen lying uncon-
scious at the bottom of a well or pit used for storing grain, an attempt should
be made to discharge oxygen from an oxygen holder into the bottom of the
well or pit by means of a hose that it may not only revivify the patient but
displace the carbon dioxide, so that others can descend to render him help.
Post-mortem Appearances.—The body heat is retained for a longer
period. The^face is usually paleTmd placid, but may be swollen and
cyanosed. The pupils are dilated. ^ TheJ^rain and lungs are deeply con-
gested. The right side of the heart contains dark fluid blood with venous
engorgement, and the left is empty. Ecchymosed patches are noticed in the
small intestine. The other internal organs are dark in colour and congested.